In his youth he travelled through Europe, studying at Venice and Padua, and at Geneva where he came under the influence of the reformed faith as represented by John Calvin. In 1602 he was elected Patriarch of Alexandria, and in 1621 Patriarch of Constantinople.

Due to Turkish oppression combined with the proselitisation of the Orthodox faithful by Jesuite missionaries, there was a shortage of schools which taught the Orthodaox faith and Greek language. Catholic schools were set up and Catholic Churhes were built next to Orthodox ones and since Orthodox priests were in short demand something had to be done. Due to good relations with the Anglicans, in 1677 Bishop Henry Compton of London built a church for the Greek Orthodox in London but in 1682 the Greek Orthodox Church in London closed. But in 1694 renewed sympathy for the Greeks drew up plans for Worcester College, Oxford (then Gloucester Hall) to become a college for the Greeks but never came to fruition.

In 1753 the Patriarch Cyril Lukaris opened a school of thought called Athoniada at Mount Athos, but the Orthodox and Catholics insisted to the Turkish authorities that this should be closed. In 1759 the Athos School was closed. The next option was to send students abroad to study, as long as it was not Catholic thought. The Calvinists were appealing because their beliefs were very similar to Orthodox ones.

It is alleged that the great aim of his life was to reform the Church on Calvinistic lines, and to this end he sent many young Greek theologians to the universities of Switzerland, the northern Netherlands and England. In 1629 he published his famous Confessio (Calvinistic in doctrine), but as far as possible accommodated to the language and creeds of the Orthodox Church. It appeared the same year in two Latin editions, four French, one German and one English, and in the Eastern Church started a controversy which culminated in 1691 in the convocation by Dositheos, patriarch of Jerusalem, of a synod by which the Calvinistic doctrines were condemned.

Cyril was also particularly well disposed towards the Anglican Church, and his correspondence with the Archbishops of Canterbury is extremely interesting. It was in his time that Mitrophanis Kritopoulos - later to become Patriarch of Alexandria (1636-1639) was sent to England to study. Both Lucaris and Kritopoulos were lovers of books and manuscripts, and many of the items in the collections of books and these two Patriarchs acquired manuscripts that today ‘adorn’ the Patriarchal Library.

Lucaris was several times temporarily deposed and banished at the instigation of his orthodox opponents and of the Jesuits, who were his bitterest enemies. Finally, when the OttomanSultanMurad III was about to set out for the Persian War, the patriarch was accused of a design to stir up the Cossacks, and to avoid trouble during his absence the sultan had him killed by the Janissaries in June 1637. His body was thrown into the sea, recovered and buried at a distance from the capital by his friends, and only brought back to Constantinople after many years.

The orthodoxy of Lucaris himself continued to be a matter of debate in the Eastern Church, even Dositheos, in view of the reputation of the great patriarch, thinking it expedient to gloss over his heterodoxy in the interests of the Church.